Feeding is inhibited by sublethal concentrations of toxicants and by heat stress in the nematode Caenorhabditis elegans: Relationship to the cellularstress response

We report that the free-living nematode Caenorhabditis elegans can respond to a variety of stressors (compounds known to induce the production of cell ular stress proteins in model biological systems), by ceasing pharyngeal pu mping. This phenomenon results in both a reduction in intake of the stresso r and a cessation of feeding. The effect of stressors can therefore be conv eniently assayed by monitoring the decrease in the density of the bacterial food in liquid cultures of nematodes. A great range of stressors induced t his response including alcohols, heavy metals, sulfhydryl-reactive compound s, salicylate, and heat. For several of these stressors, inhibition of phar yngeal pumping occurred at stressor concentrations below the threshold requ ired for the induction of the 16-kDa heat shock proteins. Salicylate, which did not induce 16-kDa heat shock proteins at any concentration, neverthele ss inhibited pharyngeal pumping. Heat was also inhibitory, at a temperature where 16-kDa heat shock protein production was near maximal. Some compound s caused only a partial inhibition of feeding while with others the effect was complete. Upon removal of the stressor, the nematodes resumed pharyngea l pumping with a residual inhibitory effect that depended on the concentrat ion and type of stressor that had been applied. A number of C. elegans neur osensory mutant strains also exhibited a cessation of pharyngeal pumping wh en exposed to stressors suggesting that the mechanism underlying this inhib ition was not entirely neurosensory and may be intrinsic to the pharynx. In C. elegans and other invertebrates, stress-induced inhibition of feeding m ay be an important survival mechanism that limits the intake of toxic solut es. J. Exp. Zool. 284:147-157, 1999. (C) 1999 Wiley-Liss, Inc.